1. The Field of the Invention
Implementations of the present invention relate generally to drilling devices and methods that may be used to drill geological and/or manmade formations. In particular, implementations of the present invention relate to core barrel assemblies and to mechanisms for latching core barrel assemblies to a drill string.
2. The Relevant Technology
Exploration drilling can include retrieving a sample of a desired material (core sample) from a formation. Wireline drilling systems are one common type of drilling system for retrieving a core sample. In wireline drilling process, a core drill bit is attached to the leading edge of an outer tube or drill rod. A drill string is then formed by attaching a series of drill rods that are assembled together section by section as the outer tube is lowered deeper into the desired formation. A core barrel assembly is then lowered or pumped into the drill string. The core drill bit is rotated, pushed, and/or vibrated into the formation, thereby causing a sample of the desired material to enter into the core barrel assembly. Once the core sample is obtained, the core barrel assembly is retrieved from the drill string using a wireline. The core sample can then be removed from the core barrel assembly.
Core barrel assemblies commonly include a core barrel for receiving the core, and a head assembly for attaching to the wireline. Typically, the core barrel assembly is lowered into the drill string until the core barrel reaches a portion the outer tube or distal most drill rod. At this point a latch on the head assembly is deployed to restrict the movement of the core barrel assembly with respect to the drill rod. Once latched, the core barrel assembly is then advanced into the formation along with the drill rod, causing material to fill the core barrel.
One potential challenge can arise due to the interaction between the core barrel assembly and the drill string. For example, when the drill string is spinning, the inertia of the core barrel assembly can exceed the frictional resistance between the mating components such that the head assembly rotates at a lower rate than the drill rod or fails to rotate and remains stationary. In such a situation, the mating components can suffer sliding contact, which can result in abrasive wear.
Accordingly, there are a number of disadvantages in conventional wireline systems that can be addressed.